Question 357301
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Hi,
The standard equation of a circle with center C(h,k) and radius r is :
{{{(x - h)^2 + (y - k)^2 = r^2}}} 
completing the square
x^2+y^2+8x-8y+16=0
x^2+ 8x +16 + y^2-8y +16 -16=0
(x +4)^2 + (y-4)^ = 16
Center of the circle is Pt(-4,4) and the circle has a radius of 4
{{{drawing(300,300, -10, 10, -10, 10,
circle(-4, 4, 4),
circle(-4, 4,0.2),
graph( 300, 300, -10, 10, -10, 10))}}}